4.2 High-Resolution PWM with Fine Edge Placement
The trigger mechanisms are summarized in Table 4-2. PWM generators are set up to run at 100 kHz with defined dead times. The PWM generators’ setup is such that it is optimized to run purely in core independent peripherals for PSFB-CDR.
More details are available in the MCC and MPLAB project.
For more information, refer to the High-Speed PWM Family Reference Manual (DS70000323).
| PWM Generator Number | Details | Function | Start of Cycle Trigger | Peripheral Setting |
|---|---|---|---|---|
PWM Generator 1 (PG1) | Complimentary PWM at 100kHz at 50% duty cycle | Generating signals for the fixed leg of PSFB | Self-Triggered | PG1 end of cycle |
PWM Generator 3 (PG3) | Complimentary PWM at 100kHz at 50% duty cycle | Generating signals for the phase-shifted leg of PSFB | Phase delayed and synchronized to PG1 | Trigger value from PG1 |
PWM Generator 2 (PG2) | Complimentary PWM at 100kHz, Swapped. Only high-side signal used | Generating the synchronous rectifier signal for SR2 | Synchronized to PG3. Duty Cycle = Period – Phase Delay | Trigger value from PG3 and swapping the high and low-side signal. |
PWM Generator 4 (PG4) | Complimentary PWM at 100kHz, Swapped. Only high-side signal used | Generating the synchronous rectifier signal for SR1 | Synchronized to PG1. Duty Cycle = Period – Phase Delay | Trigger value from PG1 and swapping the high and low-side signal. |
The control signal to the Power stage is the phase-shift value between the fixed and phase-shifted legs. The primary side switches are turned on and off using dsPIC33CK’s High Resolution PWM with the fine-edge placement peripheral. This peripheral is highly versatile, enabling the execution of complex modulation schemes independently within the controller's core-independent peripheral. In the Phase-Shifted operation the phase-shifted leg is synchronized with the fixed leg. A delay or a phase shift is introduced to induce a bipolar voltage at the transformer using a highly versatile trigger. This phase shift is the control output from the compensator to the Power stage.